The general gist is that it's a being (possibly) from another dimension that thrives in the absence of sound. It's sentient and can be conversed with.

This SCP is supposed to be based on the fact that silence seems to be a intangible thing that people can be afraid of (your heartbeat in your ears when nothing else is going on, that ringing that happens when it's quiet). (I'm still cooking up ideas on how or why the SCP in itself is Keter-class deadly.)

But the thing is, one of the points that make it dangerous is the fact that this being isn't something we can perceive since it's supposed to be silence, or the lack of sound.